A 2D model for hydrodynamics and biology coupling applied to algae growth simulations

TL;DR

This paper presents a multilayer 2D model coupling hydrodynamics and algae biology to simulate and analyze algae growth in raceway ponds, aiding optimization of biofuel production processes.

Contribution

It introduces a multilayer Saint-Venant and biological model incorporating light effects, with an efficient numerical scheme for simulating complex algae-hydrodynamics interactions.

Findings

Model can distinguish between mixed and calm water conditions

Simulation captures heterogeneity in pond environments

Velocity fields enable analysis of light exposure on algae

Abstract

Cultivating oleaginous microalgae in specific culturing devices such as raceways is seen as a future way to produce biofuel. The complexity of this process coupling non linear biological activity to hydrodynamics makes the optimization problem very delicate. The large amount of parameters to be taken into account paves the way for a useful mathematical modeling. Due to the heterogeneity of raceways along the depth dimension regarding temperature, light intensity or nutrients availability, we adopt a multilayer approach for hydrodynamics and biology. For free surface hydrodynamics, we use a multilayer Saint-Venant model that allows mass exchanges, forced by a simplified representation of the paddlewheel. Then, starting from an improved Droop model that includes light effect on algae growth, we derive a similar multilayer system for the biological part. A kinetic interpretation of the whole system results in an efficient numerical scheme. We show through numerical simulations in two dimensions that our approach is capable of discriminating between situations of mixed water or calm and heterogeneous pond. Moreover, we exhibit that a posteriori treatment of our velocity fields can provide lagrangian trajectories which are of great interest to assess the actual light pattern perceived by the algal cells and therefore understand its impact on the photosynthesis process.